The present invention relates to a thermal recording apparatus and more particularly to a thermal recording apparatus for use with a facsimile apparatus.
In general, in an image information recording apparatus, such as a facsimile apparatus employing a thermal head, numerous thermal resistors are arranged in the thermal head. For instance, when image information is recorded on an A-4 size record sheet, normally 1728 thermal resistors are arranged per line in the thermal head, and, in the case of a B-4 size record sheet, as many as 2048 thermal resistors are used per line in the thermal head, with electric power being selectively supplied to those thermal resistors, depending upon the image information to be recorded. Furthermore, it is required that the electric energy supplied to the thermal resistors be constant. Otherwise, the heating value of each thermal resistor may vary, causing the image density of the image information recorded on the record sheet to become uneven.
Conventionally, in order to supply electric power of a constant, predetermined value to those thermal resistors regardless of the number of thermal resistors to be activated, a D.C. regulated power supply with a large power capacity is employed. Such a D.C. regulated power supply system is poor in power efficiency and much electric power is wasted within the power supply system. In addition, a large radiator or a cooling-fan for dispersing heat generated in the power supply system is required. As a result, the image information recording apparatus employing such a D.C. regulated power supply is oversized and expensive.